When the terrorist bombs were exploding in London, Sarah and Thomas Mueller were chatting about their successful work in the End African Hunger campaign.

They were fresh from a pep rally Live 8 concert the night before in Edinburgh, Scotland, that had capped the campaign. Performers like Bono and James Brown had given a rousing finale. Their optimism that world leaders would help the African poor and ill was riding high. They were waiting to board a 45-minute flight to London. Walking to the boarding area, the bad news suddenly flashed on a big television monitor. Shortly thereafter, police with machine guns came marching by.

Thursday morning, bombs on three subway trains and one double-decker bus killed dozens of people and wounded more than 700. The attacks appeared to have been timed to coincide with the first day of the G8 summit talks led by British Prime Minister Tony Blair at Gleneagles near Edinburgh. An Islamist organization calling itself the "Secret Organization—Al Qaeda in Europe" has claimed responsibility for the bombings, boasting, "Here is Britain now burning with fear and terror."

Arriving in London, the Muellers found public transportation shut down but relative calm at the airport. Along with other American evangelicals on the flight, they had been beckoned to Edinburgh by the call of Bono, front man for the rock group U2, to join the "One Campaign" to persuade leaders of the richest countries to increase efforts to stop poverty and disease in Africa. Rock & roll artists themselves, the Muellers had joined Bono's antipoverty group DATA. Evangelicals on the flight also came from World Vision, Bread for the World, and other groups.

To their mainstay activity of evangelism, evangelicals are increasingly ...